Fluid pumping systems use motor drives to drive motors and pumps and transfer fluids. Fluids include liquids and gases, such as air. Fluid pumping systems are used in water wells, to extract liquids and gases from the earth, to boost pressures in pipelines, to transfer air and cooling liquids in HVAC systems, and in many other applications.
Motor drives may comprise variable frequency drives and other types of drives. Generally, an input voltage is provided to the motor drive and the motor drive converts the input voltage to a motor voltage to control the speed of the motor. In a variable frequency drive a typical input voltage is a constant frequency AC voltage, which is converted to DC voltage and the DC voltage is inverted to variable frequency AC voltage, Thus, a motor drive may include a converter, such as a bridge rectifier, a power factor correction circuit (PFC), and an inverter, which includes gated power switches. The inverter and the converter generate heat, which may be significant, due to switching inefficiencies and impedances of the components which rectify or invert the voltages.
It is known to mount individual semiconductor power components (e.g. diode, MOSFET, IGBT, BJT, Thyristor, GTO or JFET) on a circuit board. Each individual semiconductor power component has an individually packaged semiconductor power die and may be referred to as a discrete power component. A discrete power switch, such as an IGBT, may also comprise an antiparallel or freewheeling diode connected to its power leads. Accordingly, discrete power components generally comprise two power leads with or without a control or gate lead. Individually mounting discrete power components requires additional steps to mount each discrete power component in a way that insulates the remaining components of the circuit board, which typically include low-voltage control components, electrically and thermally.
Power modules are also known. In a power module multiple semiconductor power dies are connected together in a single package and are arranged in various topologies. Examples of power module modules include bridge rectifiers containing four (single-phase) or six (three-phase) diodes, H-Bridges (four switches and the corresponding antiparallel diodes), boost or power factor correction circuits (switches with antiparallel diodes and high frequency rectifying diodes), and three-phase inverters (six switches and corresponding antiparallel diodes). Power modules are sold in standard topologies and power ratings.
Improvements are desirable to increase the reliability and availability, and to lower the cost of motor drives.